1. Field Of The Invention
The present invention relates to bypass devices for relieving pressure on inflatable packers in a tool string, and more particularly, to a packer bypass having a bypassing mandrel therein which can be reset for reinflating the packers.
2. Description Of The Prior Art
In testing a well formation, a testing string is lowered into a well bore such that a packer is positioned above and below the formation to be tested. The packers are typically of the inflatable type and a pump in the testing string is actuated for pumping fluid to inflate the packers into sealing engagement with the well bore for isolation of the formation. When testing is completed, it is necessary to bypass or vent the fluid in the packers back to the well annulus so that the testing string may be moved to a different location in the well bore or removed therefrom.
A typical packer used is the Halliburton Hydroflate.RTM. packer, manufactured by the assignee of the present invention, and disclosed in Halliburton Services Catalog 43, pages 2537-2538. The pump previously used with this packer has a built-in packer bypass which releases fluid from the packers when pull is exerted on the bypass from the surface.
A tester valve is used which also requires manual manipulation from the surface, and a problem with the previous packer bypass is that overpull on the tester valve may result in premature actuation of the packer bypass with resulting premature deflation of the packers.
The present invention solves this problem by providing a packer bypass with a mandrel having a pressure differential thereacross which requires approximately 10,000 pounds pull to actuate during a packer deflation operation. This force is greatly more than is needed to operate the tester valve. Thus, even if there is some overpull on the tester valve, premature actuation of the packer bypass is not likely to occur.
The mandrel in the packer of the present invention is automatically released when in a bypass position so that it can reclose if pump pressure is reapplied. In this way, the packer bypass may be used for sequential tests with the testing string.